Fan



N. LAING March 22, 1966 FAN 4 Sheets-Sheet 1 Filed Jan. 22, 1965INVENTOR 9 flM W 43 a? ATTORNEYS Ni koluus Lain Hil /2 h? N. LAING March22, 1966 FAN 4 Sheets-Sheet 2 Filed Jan. 22, 1965 FIGS.

INVENTOR Nikolaus Laing BYXQWMFZM W47, 7 MM fiToRNEYs March 22, 1966Filed Jan. 22, 1965 N. LAlNG FAN J f n g I n 4 Sheets-Sheet 5 INVENTORNiko uus Laing BY M, u /a, 1% X ATTORNEYS N. LAING March 22, 1966 FAN 4.Sheets-Sheet 4.

Filed Jan. 22, 1965 FIG. 10.

INVENTOR United States Patent 3,241,742 FAN Nikolaus Laing, Hofener Weg35, Aldingen, near Stuttgart, Germany Filed Jan. 22, 1965, Ser. No.427,429 Claims priority, application Germany, Mar. 11, 1960, L 35,582 20Claims. (Cl. 230-117) This application is a continuation-in-part of mycopending application No. 95,405 filed March 13, 1961 now abandoned.

This invention relates to fans and more particularly to cross-flow fans,i.e. fans of the kind comprising one or more cylindrical bladed rotorsand guide means cooperating therewith whereby on rotor rotation toinduce a flow of air from an inlet side of the rotor through the path ofthe rotating blades thereof to the interior of the rotor and thenceagain through the path of the rotating blades to an outlet side of therotor, the general direction of the flow being transverse to the rotoraxis.

It is believed that cross-flow fans were invented at the end of the lastcentury, and it has been stated that such fans were used for a time forcolliery ventilation, and later replaced by centrifugal fans. Since thattime various types of cross-flow fans have been proposed. All thesecross-flow fans, so far as can be judged from the literature, are oflarge capacity and suited only for industrial use or the like: also,they depend for their operation on the maintenance of close tolerancesbetween the rotor and the guide means. British Patent No. 876,611 (ofwhich I am co-inventor) discloses a new principle of cross-flow fandesign, especially suited to small sizes such as for domestic use, andin which the guide means are wholly external of the rotor and may withadvantage be well spaced therefrom. The disclosures of British PatentNo. 876,611 accordingly provide the basis for the design of atechnically effective and readily mass-produced domestic fan.

One important form of domestic fan is the smallcapacity compact andreadily portable fan called herein table fan which may be placed on atable or the like near the user, and produce a stream of air directed athim, eg for cooling purposes in summer. Hitherto small axial fans havebeen used for this purpose. Such fans can be produced very cheaply. Thecross-flow fan as disclosed in British Patent No. 876,611 has certaincharacteristics which would give it advantages over the axial fan, inapplication to table fans: thus, a satisfactory volume of air may bemoved at relatively low peripheral blade speed, so that noise can bereduced, and the emergent jet of air is smoother and of greaterpenetrating power than that of an axial fan, which is full of randomeddies. However, the configuration of the cross-flow fan does notimmediately adapt itself to a table fan: in any case whateverconfiguration is adopted it must be at least as convenient to use as thewell known axial fan and comparable in cost of manufacture, otherwise itcannot be expected to enjoy great commercial success. A main object ofthe invention is to provide a table fan of the cross-flow type havingthe advantages just mentioned of convenience in use and ease ofmanufacture.

With this main object in view, the invention provides a cross-flow fanhaving a flat base adapted to stand on a table, a support upstandingfrom the base and rigid therewith, a motor casing mounted on thesupport, a motor in the casing having a substantially horizontal shaft,a bladed cylindrical rotor overhung-mounted on one end of the motorshaft and projecting beyond the casing and said support, and a flowguide unit also supported on and projecting beyond said support, theflow guide unit present- Patented Mar. 22, 1966 ice ing guide surfacesopposite the rotor which co-operate therewith on rotor rotation toinduce a flow of air from one side of the rotor through the path of therotating blades thereof to the interior of the rotor and thence againthrough the path of the rotating blades to another side of the rotor.

In a preferred form of the invention, the support terminates on amounting ring the axis of which extends substantially parallel to theplane of the base; the motor casing is supported on the mounting ringand overhung in one direction therefrom, while the rotor and guide unitare overhung in the other direction clear of the casing and mountingring.

The fan unit configuration described is convenient to use and simple andeffective to manufacture. Thus in one non-adjustable form the base,support, motor casing and the major part of the guide unit may be asingle integral plastics moulding, the motor with rotor attached beingsimply push-fitted into the casing therefor. In another preferred formof the invention, the guide unit is angularly movable about the axis ofthe motor and rotor.

Other features of the invention have to do with features permittingready disassembly of the motor and rotor for cleaning of the latter.

Further features of the invention will appear from the followingdetailed description of various embodiments thereof.

In the drawings, in which:

FIGURES 1 and 2 are respectively a transverse and an axial section of aroom fan unit;

FIGURES 3a, 3b and 3c are scrap axial sections showing three differentways in which a rotor and shaft such as shown in FIGURES 1 and 2 can bedetachably assembled together;

FIGURE 4 is an axial section of a second room fan unit;

FIGURE 4a is a perspective view of part of the FIG- URE 4 unit;

FIGURES 5, 6 and 7 are diagrams illustrative of different ways in whicha rotor such as shown in FIGURE 4 can be assembled with a driving motortherefor;

FIGURE 8 is an axial section of a rotor together with means upon whichit is to be secured, the rotor being shown separate from these means;

FIGURE 8a is a partial axial section of a rotor showing means forclosing the non-driven end thereof, these means being shown separatefrom the rotor;

FIGURES 9 and 10 are respectively an axial and a transverse section of afurther form of room fan unit, and

FIGURE 11 is an end elevation of the unit of FIG- URES 9 and 10 showinga minor variation upon this unit.

Where axial and transverse sections correspond the section plane of thetransverse section is shown on the axial section with the figure numberof the transverse section in Roman numerals.

Referring to the drawings, the room fan unit shown in FIGURES 1 and 2comprises a base 1, supported upon legs 2 a housing 3 wherein is locateda motor. The motor is of conventional type and not shown and the housingis indicated simply as a block having an upper wall 3a of substantialthickness. The motor has a horizontal spindle and the two end portionsof the spindle designated 4, 4', extend symmetrically from the housingat either end thereof. Each end portion 4, 4' of the spindle is formedwith a flange 5, 5 spaced from its end, which end is formed as athreaded stub 6, 6'. A pair of similar cylindrical bladed rotors 7, 7'are mounted on the end portions 4, 4 of the spindle. Each rotorcomprises end discs 10, 11 supporting between them a series of blades12, and the end disc 11 has a tapped axial hole enabling it to bescrewed upon the corresponding 3 threaded stub 6, 6' until it comes flatagainst the flange 5,

The fan unit further comprises a guide unit 3 having two similarsections 13a, 13b, each section co-operating with one of the rotors 7,7'. The guide unit sections 13a, 13b are connected by an integralcentral portion 130 which overlies the housing 3 and is secured theretoby a milled-headed screw 14 working in a tapped hole in the wall 3a ofthe housing.

Each guide unit section 13a, 13b provides a pair of approximatelycrescent-shaped end walls 15, 16 respectively coplanar with the rotorend discs 10, 11 and joined by guide walls 17, 18. As seen in FIGURE 1the guide wall 17 is short and converges with the periphery of the rotor7 in the direction of rotor rotation indicated by the arrow 20 inFIGURE 1. The line 18a of nearest approach of the guide wall 18 to therotor 7 lies approximately diametrally opposite the line 17a of nearestapproach of the guide wall 17. At both lines 17a and 18a the respectiveguide walls 17, 18 are spaced from the rotor substantially more than aworking clearance, preferably about half the radial blade depth, orpossibly more. The wall 18 extends away from the rotor 7 with a steadyincrease in radius of curvature going from the line 18a. Guide walls 17and 18 terminate remote from the rotor in lines 17b, 1812 which definethe outlet from the unit, for the rotor 7. The plane joining the lines17b, 18b is oblique to the direction of flow through the outlet.

The blades 12 of the rotor 7 will be seen to be concave facing thedirection of rotation and to have their outer edges leading their inneredges.

In operation of the unit a cylindrical vortex having a core shown by theflow lines V is formed adjacent the guide wall 17: the vortex coreintersects the blades and lies parallel and eccentric to the axis of therotor. Air is induced to flow through the rotor as shown by the flowlines F. The principles upon which the fan unit of FIG- URES 1 and 2operates are set forth in detail in the British patent specification876,611 which should be referred to.

The flow machine of FIGURES 1 and 2 can readily be disassembled forcleaning without the use of tools by simply unscrewing the rotors 7, 7from their threaded stubs 6, 6' and removing the guide unit 13 afterunscrewing the milled-headed screw 14. The rotors 7, 7' and guide unit13 can conveniently be moulded of plastics material.

Three further ways of detachably securing a rotor to a driving shaft, inan arrangement such as that of FIG- URES 1 and 2, are shown in FIGURES3a, 3b and 30. In FIGURE 3a, a circular retainer plate 30 of greaterdiameter than the rotor 7 is formed on the end of the shaft portion inplace of the flange 5 of FIGURE 2. The adjacent end disc 11' of therotor 7 differs from the end disc 11 of FIGURE 2 in carrying a threadedprojecting boss 31 co-operating with female threads 32 formed axially ofthe retainer plate 30. The plate 30 and rotor 9 can readily be graspedin the hands when it is desired to separate them: this arrangement istherefore particularly suitable where the construction of FIGURES 1 and2 is modified to present only one rotor.

FIGURES 3b and 3c show rotors 7 detachable by snap action. In FIGURE 3bthe shaft end portion 4 is shown terminating beyond the flange 5 in acylindrical boss 33 formed with a transverse bore 33a locating a pair ofballs 34 urged outwardly by a helical compression spring 35 actingbetween them, the balls being prevented from flying out of the bore bylips 33b formed at its mouth. The rotor end disc 11" is formed with abore 11a receiving the boss 33 in a close fit, and a groove 11b openingout of the bore. The balls 34 are received in the groove 11b; the rotorcan readily be assembled and disassembled simply by exerting apronounced axial force thereon. Drive from the shaft 4 to the rotor 7 iseffected by friction, bearing in mind that only low torques areinvolved. Alternatively co-operating flats may be formed on the boss 33and end disc 11", or a projection on the flange 5 may engage a recess inthe end disc.

Parts of the FIGURE 3c construction similar to that of FIGURE 3b aregiven the same reference numerals and will not need further description.Instead of the transverse bore 33a of FIGURE 3b, the boss 33 of FIG- URE30 has a peripheral groove 36 locating a toroidally wound resilientstrip 37. Once again assembly and disassembly is effected by pronouncedaxial force such as can readily be applied manually without the aid oftools.

The fan unit of FIGURES 4 and 4a comprises a base 40, a supporting post41 upstanding from the base and mounting a motor housing 42 in the formof a cylinder with a closed end, and guide means designated generally 43which extends to one end of the motor housing. The parts so farmentioned are all moulded integrally from plastics material by means ofa four-part mould, one part of which is stationary and the other partsof which move in three directions at right angles to one another when itis required to release a completed article from the mould, the articlefinally being stripped from the stationary part. After moulding, a stripof plastics material 44 is secured across the guide means 43 e.g. byadhesive; thereafter the parts appear as shown in FIGURE 4a.

A motor 45 is push-fitted into the housing 42 and retained therein byfriction. The motor has a shaft 46 mounting a magnetic disc 47 in linewith the opening in the housing 42, this disc having a central conicalcentering projection 48. A rotor designated generally 49 and having enddiscs 50, 51 supporting blades 52 between them is mounted on themagnetic disc 47, the end disc 51 for this purpose being made ofmagnetic material and having a recess 52 co-operating with the centeringprojection 48.

The rotor 49, apart from the end disc 51, resembles the rotor 7 inFIGURES 1 and 2. The guide means 43 provides end walls 53, 54 similar tothe end walls 15, 16 of FIGURES 1 and 2, and a guide wall 55 similar tothe guide wall 18 of those figures. The strip 44 corresponds in functionto the guide wall 17 of FIGURES 1 and 2. The flow conditions in theFIGURE 4 fan unit are therefore exactly similar to those illustrated inFIGURE 1, and will require no further description.

The discs 47 and 51 can be magnetized in various ways: as shown inFIGURE 5 annular zones can be formed, the zones, going radially,alternating in polarity. Alternatively, as shown in FIGURE 6 the zonescan be sectorshaped. In the FIGURE 7 arrangement the disc designatedgenerally 47 is formed as a magnetized block 70 of cylindrical shapeassociated with a magnetic disc 71 having an axially directed peripheralflange 72; the rotor disc 51 is ferromagnetic, and magnetic circuits areset up in radial planes the flux wherein tends to hold the disc 51 up tothe disc 47.

To disassemble the fan unit illustrated it suffices to exert an axialpull on the rotor 49 to overcome the magnetic forces set up between thediscs 47 and 51; the rotor can then be washed if desired and theinterior of the guide means 43 becomes accessible for cleaning. Themotor 45 can be removed by exerting pressure on the end 75 of the shaft46 opposite the disc 47; this end 75 of the shaft projects into a smallhole 76 in the end wall of the motor housing 42. Once the motor 45 isout of the housing 42, the unit consisting of base 40, post 41, housing42 and guide means 43 can be washed.

A further method of detachably securing a rotor to a shaft is shown inFIGURE 8. The rotor, designated generally 80, is made of resilientplastics material and comprises blades 81 extending between a disc 82 atone end and a ring 83 at the other. The ring 83 has its inner peripherybevelled slightly. The shaft 84 mounts a disc 85 of resilient plasticsmaterial the periphery of which is also slightly bevelled, and the disc85 carries a steppedback flange 86 that extends radially. The meansdiameter of the inner periphery of the ring 83 is the same as the meansdiameter of the disc 85, but because of their being bevelled theiropposing edges 83a, 85a interfere. On account of the resiliency of theplastics these edges 83a, 85a can be forced past each other with a snapaction and will thereafter interengage to hold the ring 83 tight againstthe flange 86.

.FIGURE 8a shows a similar arrangement for an end closure disc at thenon-driven end of the rotor. Parts similar to those of FIGURE 8 aregiven the same reference numerals as used in that figure butdistinguished by a prime; these parts will therefore need no furtherdescription.

FIGURES 9 and 10 show a room fan unit comprising a base 90, a post 91upstanding from the base, and a support ring 92 carried by the post. Anaxial flange 93 rigid and coaxial with the ring 92 carries a series ofresilient projections 93a over which frictionally engages a motorhousing 94 in the form of a cylinder with one end closed. The supportring 92 supports a motor 95 within the housing the shaft of whichextends through the ring and carries a rotor 96 that comprises a pair ofend discs and blades supported thereby, these discs and bladesresembling those of the rotor 7 of FIGURES 1 and 2 and being designatedby'the same reference numerals 10, 11, 12 respectively. Unlike the rotor7, however, the rotor 96 includes a set of short blades 97 secured tothe side of the end disc 11 opposite the blades and forming an auxiliaryrotor of the axial-in, radial-out type. As will have been appreciatedthe projections 93a space the housing 94- from the flange 93 and permitentry of air to the interior of the housing: the auxiliary rotor formedby the blades 97 ejects air from the housing 94 and sets up acirculation as indicated by the arrows 98.

A one-piece guide unit 99 co-operates with the rotor 96 and differs fromone of the guide unit sections 13a, 13b of FIGURE 1 only in the methodof its support: the parts of the unit 99 are therefore given the samereference numerals as those of FIGURES l and 2 and will need no furtherdescription. The guide unit 99 and rotor 96 co-operate to induce flow asdescribed with reference to FIGURES 1 and 2. The unit 99 is simplyrested on a radial flange 100 forming an extension of the ring 92 andheld in place by interengagement with that extension, as by means oflugs 99a formed integrally with the guide unit end wall 16, the flange100 being gripped between this end wall and the lugs. The guide unit 99is angularly movable about the axis of the motor 95 and rotor 96 andretained in adjusted position by friction between the end wall 16 andlugs 99:: on the one hand and the flange 100 on the other. Other meansof releasably attaching the unit 99 to the support ring 92 may bedevised by those skilled in the art.

The various parts of this fan unit, with of course the exception of themotor 95, can conveniently be made from sheet metal; the motor casing94, guide unit 99 and base 90 could alternatively be made with advantagein plastics. To disassemble the fan unit it is merely necessary to liftoff the guide unit 99 and pull off the motor housing 92 against thefriction applied therto by the projections 93a. The rotor 96 is alsoreadily detachable as described above.

FIGURE 11 shows a modification of the fan unit of FIGURES 9 and 10wherein the end wall 16 of the guide unit 99 overlies the end disc 10instead of being coplanar therewith.

I claim:

1. A portable domestic fan having a flat base adapted to stand on atable, a support upstanding from the base and rigid therewith, a motorcasing mounted on the support, a motor in the casing having asubstantially horizontal shaft, a bladed cylindrical rotoroverhung-mounted on one end of the motor shaft and projecting beyond thecasing and said support, and a one-piece flow guide unit also supportedon and projecting beyond said support,

the flow guide unit presenting guide surfaces opposite the rotor whichco-operate therewith on rotor rotation to induce a flow of air from oneside of the rotor through the path of the rotating blades thereof to theinterior of the rotor and thence again through the path of the rotatingblades to another side of the rotor.

2. A fan as claimed in claim 1, wherein the motor casing is centrallydisposed with respect to the base and carries two similar rotors one oneach end of the motor shaft and two guide units are provided whichproject to either side of the motor casing for co-operation with therespective rotors.

3. A fan as claimed in claim 2, wherein the guide units areinterconnected by a central connecting portion overlying the motorcasing and detachably connected thereto.

4. A fan as claimed in claim 1, wherein the rotor has its bladessupported between a pair of imperforate end discs.

5. A fan as claimed in claim 4, wherein the motor shaft has a flangeadjacent the rotor, the rotor is connected to the motor shaft by a screwconnection with one rotor end disc, the end disc when fully screwed tothe shaft abutting the flange thereon.

6. A fan as claimed in claim 5, wherein the flange has at least the samediameter as the rotor end disc whereby both may be grasped manually.

7. A fan as claimed in claim 4, wherein the motor shaft has a bosscarrying outwardly urged locating elements releasably received in onerotor end disc.

8. A fan as claimed in claim 4, wherein the motor shaft has a flangeadjacent the rotor which contacts one rotor end disc, the flange and enddisc having co-operating magnetic means holding the end disc releasablyto the flange.

9. A portable domestic fan having a flat base adapted to stand on atable, a support upstanding from the base and rigid therewith, a motorcasing mounted on the support and overhung in one direction therefrom, amotor in the casing having a substantially horizontal shaft, a bladedcylindrical rotor mounted on one end of the rotor shaft and overhungthereon in the other direction beyond the casing and said support, and aflow guide unit also supported on and overhung beyond said support insaid other direction, the flow guide unit presenting guide surfacesopposite the rotor which co-operate therewith on rotor rotation toinduce a flow of air from one side of the rotor through the path of therotating blades thereof to the interior of the rotor and thence againthrough the path of the rotating blades to another side of the rotor.

10. A fan as claimed in claim 9, wherein the base, motor casing and themajor part of said guide unit are a single plastics moulding.

11. A fan as claimed in claim 9, wherein the rotor has its bladessupported between a pair of imperforate end discs.

12. A fan as claimed in claim 11, wherein the guide unit comprises apair of end walls interconnected by a side wall extending the length ofthe rotor, the end walls forming endwise extending guide surfaces forair leaving the rotor, the end wall remote from the motor being coplanarwith the corresponding rotor end disc and defining an arcuate edgeoverlying an arc thereof in closely spaced relation.

13. A fan as claimed in claim 9, wherein the guide unit comprises a pairof end walls located at either end of the rotor and a pair of side wallsinterconnecting said end walls and defining an outlet from the rotor.

14. A fan as claimed in claim 13, wherein the guide unit is supported bythe end wall adjacent the motor casing.

15. A fan as claimed in claim 9, wherein the rotor includes an end discadjacent the motor, a series of main blades supported on the end disc,said main blades being arranged in a ring centred on said axis andextending parallel thereto and away from the motor, a series ofauxiliary blades also supported on the end disc and extending towardsthe motor, said casing having a peripheral inlet opening and a centraloutlet opening facing said auxiliary blades and said auxiliary blades inoperation setting up by centrifugal fan operation a cooling air currentflowing between said openings which current is independent of the airflow through the main rotor blades.

16. A portable domestic fan having a fiat base adapted to stand on atable, a support upstanding from the base and rigid therewith andterminating in a mounting ring the axis of which extends substantiallyparallel to the plane of the base, a motor casing supported on themounting ring and overhung in one direction therefrom, a motor in thecasing having a substantially horizontal shaft coaxial with the mountingring, a bladed cylindrical rotor mounted on one end of the motor shaftand overhung thereon in the other direction clear of the casing and saidmounting ring, and a flow guide unit also supported on and overhungclear of said mounting ring in said other direction, the flow guide unitpresenting guide surfaces opposite the rotor which co-operate therewithon rotor rotation to induce a flow of air from one side of the rotorthrough the path of the rotating blades thereof to the, interior of therotor and thence again through the path of the rotating blades toanother side of the rotor.

17. A fan as claimed in claim 16, wherein the flow guide unit isrotatable with respect to the mounting ring to vary the direction of airflow out from the rotor.

18. A fan as claimed in claim 16, wherein the rotor comprises a pair ofend discs and a series of blades arranged in a ring about the axis andsupported onthe end discs and the How guide unit comprises a pair of endwalls at either end of the rotor, a pair of side walls interconnectingthe end walls and providing the aforesaid guide surfaces, the side wallsand end walls defining an outlet for flow from the rotor, and the endwall remote from the motor is coplanar with the corresponding end discand defines an arcuate edge closely overlying an arc of the end disc.

19. A fan unit comprising a plate-like base, a support upstanding fromthe base and rigid therewith, said support terminating in a mountingring the plane of which extends at right angles to the plane of thebase, an electric motor supported on the mounting ringvin overhungrelation thereto and on one side thereof, the motor having a shaftaligned on the axis of the mounting ring, a casing around the motor, acylindrical bladed rotor supported coaxially on the motor shaft inoverhung relation to the motor and on the opposite side of the mountingring to said motor, and guide, means supported on the mounting ring inoverhung relation thereto and extending the length of the rotor, saidguide means co-operating with the rotor to guide air twice through theblades of the rotor in a direction transverse to the rotor axis, onoperation of the motor, said rotor including an end disc adjacent themotor, a series of main blades supported on the end disc, said mainblades being arranged in a ring centred on said axis and extendingparallel thereto and away from the motor, a series of auxiliary bladesalso supported on the end disc and extending towards the motor, saidmounting ring, motor and easing defining a first opening to the interiorof the casing at the ring end thereof and adjacent the blades, saidcasing having also a second opening, and said auxiliary blades inoperation setting up a cooling air current flowing between said openingswhich current is independent of the air flow through the main rotorblades.

20. A fan unit comprising a plate-like base, a support upstanding fromthe base and rigid therewith, said support terminating in a mountingring the plane of which extends at right angles to the plane of thebase, an electric motor supported on the mounting ring in overhungrelation thereto and on one side thereof, the motor having a shaftaligned on the axis of the mounting ring, a casing around the motor, acylindrical bladed rotor supported coaxially on the motor shaft inoverhung relation to the motor and on the opposite side of the mountingring to said motor, and guide means supported on the mounting ring inoverhung relation thereto and extending the length of the rotor, saidguide means co-operating with the rotor to guide air twice through theblades of the rotor in a direction transverse to the rotor axis, onoperation of the motor, said rotor including a pair of end discs, aseries of blades supported between the end discs, said blades beingarranged in a ring about the axis of the motor shaft and extendingparallel thereto, said guide means including parallel end walls andguide walls extending between and rigid with the end walls, the end wallremote from the mounting ring closely overlying an arc of thecorresponding rotor end disc and being radially aligned therewith.

References Cited by the Examiner UNITED STATES PATENTS 1,366,519 1/1921Carmean et al. 2301l7 1,950,768 3/1934 Anderson 230 2,768,316 10/1956Neiss 64-30 2,814,432 11/1957 Eiserman 2301 17 2,881,602 4/1959 Baker eta1. 64-29 FOREIGN PATENTS 559,024 1/1958 Belgium.

ROBERT M. WALKER, Primary Examiner.

1. A PORTABLE DOMESTIC FAN HAVING A FLAT BASE ADAPTED TO STAND ON ATABLE, A SUPPORT UPSTANDING FROM THE BASE AND RIGID THEREWITH, A MOTORCASING MOUNTED ON THE SUPPORT, A MOTOR IN THE CASING HAVING ASUBSTANTIALLY HORIZONTAL SHAFT, A BLADED CYLINDRICAL ROTOROVERHUNG-MOUNTED ON ONE END OF THE MOTOR SHAFT AND PROJECTING BEYOND THECASING AND SAID SUPPORT, AND A ONE-PIECE FLOW GUIDE UNIT ALSO SUPPORTEDON AND PROJECTING BEYOND SAID SUPPORT, THE FLOW GUIDE UNIT PRESENTINGGUIDE SURFACES OPPOSITE THE ROTOR WHICH CO-OPERATE THEREWITH ON ROTORROTATION TO INDUCE A FLOW OF AIR FROM ONE SIDE OF THE ROTOR THROUGH THEPATH OF THE ROTATING BLADES THEREOF TO THE INTERIOR OF THE ROTOR ANDTHENCE AGAIN THROUGH THE PATH OF THE ROTATING BLADES TO ANOTHER SIDE OFTHE ROTOR.